The present invention relates to the art of diagnostic equipment. It finds particular application in conjunction with a mobile x-ray unit and will be described with particular reference thereto. However, it is appreciated that the present invention may also be applicable to other environments in which support of diagnostic equipment is required.
Diagnostic equipment such as x-ray sources are typically mounted on a boom or movable arm to allow selective positioning of the source relative to a patient. The x-ray source is attached at one end of the arm and because of the weight of the source, the arm is usually biased to support the x-ray source.
Conventional x-ray units employ mechanical springs such as coil or helical springs to bias the arm in a direction opposite from the force or load imposed on the arm by the x-ray source. The spring is designed to counteract all or substantially all of the weight of the source, depending on the design of the support equipment. These counterbalance assemblies require a large mechanical spring to counteract the weight of the x-ray source and permit an operator to easily position the source as needed. Additionally, these mechanical spring arrangements generally have a small energy to unit weight ratio necessitating a large spring that results in a correspondingly large structure.
Still other drawbacks are associated with the use of springs of this type as counterbalance assemblies. Oftentimes, the x-ray source is designed for selective removal from the end of the arm. Care must be used to assure that the arm is stabilized and secured while the source is removed. Otherwise, the biasing force of the mechanical spring is unrestrained once the weight of the source, that normally opposes the biasing force, is removed.
Another problem associated with the use of mechanical springs as the biasing arrangement in prior devices is the lack of controlled movement. Usually, the spring counteracts or supports the dead weight of the source so that even small forces provide relative ease of movement. At first glance, this may not appear to be a problem. Unfortunately, the problem is magnified if the spring fails and no counteractive force is imposed on the arm to balance the weight of the x-ray source. The source or anything disposed in the path of the source could be subjected to damage from such uncontrolled movement.
In accordance with the present invention, a new and improved counterbalance assembly is provided to support the diagnostic equipment. The new and improved counterbalance assembly also provides for controlled movement of the x-ray unit, even if the biasing arrangement fails.